Interspecific Cornus hybrid designated KN30-8

ABSTRACT

An advanced generation interspecific hybrid of ( Cornus kousa×C. nuttallii ) that is distinguished by its exceptionally high vigor, superior foliage, floriferous display of very attractive and exceptionaly large white floral bracts, high level of winter hardiness, good drought tolerance and high resistance to the incitants of powdery mildew and dogwood anthracnose.

Botanical designation: (Cornus kousa×C. nuttallii)×C. kousa.

Variety denomination: KN30-8

BACKGROUND OF THE INVENTION

This new cultivar is the product of a long standing detailed program of interspecific hybridization and selection of dogwoods, in this instance a cross of an F₁ interspecific hybrid of a Cornus kousa×C. nuttallii backcrossed to an unrelated Cornus kousa. The progeny were carefully retained and characteristics analyzed for their differences and outstanding value as potential commercial varieties or cultivars.

We have selected the particular seedling hereof from certain progeny grown in a cultivated area and, as a result, have in turn caused the same to be asexually reproduced by grafting (usually T-budding or chip-budding). It also can be propagated by softwood cuttings. The reproduction and actual growth and selection of the new cultivar took place in the vicinity of New Brunswick, N.J. and has been found to be distinctive as to its winter-hardiness in that area, USDA Plant Hardiness Map Zone 6a.

As will be understood from the detailed description of the invention which appears hereinafter, the new cultivar is in fact outstanding and readily identified as being such. With the foregoing in mind, the description which follows will be understood as clearly defining the new cultivar, the desirable characteristics of which are the result of such a program as has been heretofore suggested.

SUMMARY OF THE INVENTION

The variety was originated or discovered on Horticulture Farm No. 1 of Rutgers University, New Brunswick, N.J. 08901, Middlesex County. This seedling resulted from a controlled cross made Jun. 2, 1983, between an unpatented hybrid Cornus kousa×C. nuttallii plant (seed parent) and a C. kousa plant (pollen parent). The complete parentage of the claimed plant can be summaed as follows: (Cornus kousa ‘Chinensis’×C. nuttallii ‘Goldspot’)×C.kousa ‘Rosea’.

The antecedent cultivars ‘Chinensis’, ‘Goldspot’ and ‘Rosea’ are all unpatented.

The seedling which became this new variety germinated during April 1984, was transplanted ftom the seedling flat to a one-gallon container in May 1984 and subsequently grown in progressively larger containers until April 1986, when it was transplanted to field No. 20 at the animal research farm of the NJ Agricultural Experiment Station in North Brunswick, N.J. and is growing there now as a 20-year-old tree. It has also been propagated by nurserymen in Tennessee, Oregon, and California under formal testing agreement with the NJAES, Cook College/Rutgers University. To the best of our knowledge, this new variety is the first reported advanced generation interspecific hybrid of these two species.

BRIEF DESCRIPTION OF THE DRAWINGS

This new cultivar of dogwood is illustrated by the accompanying photographic drawings, depicting the plant by the best possible color representation using color photography. All color references below are measured against The Royal Horticultural Society (R.H.S.) Colour Chart. Colors are approximate as color depends on horticultural practices, such as light level and fertilization rate, among others.

FIG. 1 shows a dogwood tree of the present invention after 20 growing seasons; and

FIG. 2 shows a single flower head of the tree shown in FIG. 1 taken at the time of floral display, and indicates the color and shape of the floral bracts.

BOTANICAL DESCRIPTION OF THE INVENTION PLANT

-   Form: Tree. -   Growth habit: Dense tree branched low to ground with upright     branches which form a rounded head wider than tall. Very vigorous.     -   -   Height.—5.48 meters at 20 years.         -   Spread.—6.55 meters at 20 years. -   Plant vigor: Plants of this new hybrid variety are much more     vigorous than plants of current varieties known to the inventors     of C. kousa. One year budded liners (either C. kousa or C. florida     rootstock) produced in either Boring, Oreg. or Winchester, Tenn.     have averaged 1.2 meters tall and are stout and branched. -   Cold hardiness: Original seedling has suffered no winter injury     during the 18 years it has been observed in the field at North     Brunswick, N.J. in USDA Plant Hardiness Map Zone 6a (−5° to −10°     F.). -   Resistance to insects and disease: No insect or disease problems     were observed during the 18 years the original seedling of the     variety ‘KN30-8’ has been tested in the field. -   Trunk: Circumference of the crown of the original seedling at the     soil level was 1.35 m after 20 growing seasons.     -   -   Color.—Between 197C and 197D Greyed-Green Group.         -   Texture.—Sandpaper rough, bark exfoliating at basal 0.46 m             of trunk area. -   Branches:     -   -   Color.—Closest to 200B, Brown Group.         -   Texture.—Smooth, with small rough bumps (lenticels).         -   Crotch angle.—45°.         -   Lenticels.—Abundant. The average (n=4) of lenticels per cm²             is 103.75 based on a range of 4 sample areas between 74             cm²-164 cm².         -   Internode length.—6.5-15 cm.

FOLIAGE

-   Leaf arrangement: Opposite. -   Leaf size — blade:

Year n average length (cm) average width (cm) 1998 25 13.24 7.68 2001 26 10.59 5.99 2002 10 15.30 9.09 Wherein n are the number of observations

-   -   -   Shape.—Oval to obovate.         -   Tip.—Apiculate.         -   Base.—Attenuate-acuminate.         -   Margin.—Mildly wavy.

-   Texture: Leaves heavily textured with prominent midrib on abaxial     surface; average of 5, sometimes 6, secondary vein pairs. Both     surfaces downy, more so beneath, due to many fine, short, whitish     hairs.

-   Other features: Dense tufts of long, brown hairs at axils of the     uppermost 3-4 vein pairs.

-   Quantity: Many, densely foliaged.

-   Coloration: Solid.

-   Mature foliage color — adaxial: 139A Green Group. Abaxial: 137C     Green Group.

-   Autumn foliage color at New Brunswick, N.J.:     -   -   Adaxial surface.—September 10 through October — 137A Green             Group; November — Foliage quite attractive but leaves at             base of tree and interior of plant green (137A Green Group).             Other leaves still predominantly green but mottled with             other colors: mostly 187A and 185A Greyed Purple Group with             a mottle of 13A Yellow, 17C Yellow-Orange, 42A Red, and 46A             Red.         -   Abaxial surface.—138C Green Group.             Leaf color is clearly dependent on many environmental             factors such as soil type, exposure to sun, air temperature,             day length, available water and nutrients. Thus, leaf color             may vary from one area to another. Veins and ribs: The basal             3-4 cm of the midrib of the leaves sometimes shows a little             yellow streak closest to Yellow-Group 8D.

-   Petiole: Color at New Bunswick, N.J.     -   -   May.—144B Yellow-Green Group.         -   June.—143C Yellow-Green Group.         -   September.—145A Yellow-Green Group.         -   October.—144A Yellow-Green Group with a little 47B Red Group             and 53A Red Group.

-   Disease resistance: Asexually propagated plants of our new hybrid     variety have been tested in New Brunswick, N.J. (18 years) and in     Boring, Oreg. and Winchester, Tenn. (10 years) with no evidence of     susceptibility to Powdery Mildew or Dogwood Anthracnose.

INFLORESCENCE

-   Location where observations were made: Animal Research Farm, NJAES,     North Brunswick, N.J. -   Type of inflorescence: Flower head. Dense, rounded mound. -   Over-wintering flower buds: 5.6 mm high and 6.3 mm wide (n=10     measurements taken). -   Peduncle: In winter months, 1-2 cm long and 3.1 cm wide. Is     completely covered, or enclosed, by typically 2, sometimes 3, pairs     of opposing, appressed bracts approximately 9.1 mm long and 7.6 mm     wide. These vegetative bracts are closely telescoped on the     peduncle, are uniformly wide at the basal 60 percent, close in     slightly and taper to a blunt apex. Their color is 185A     Greyed-Purple at base and center and 177B Grey-Orange at the tips     and along the margins. -   Size at time of flowering — (late May — early June):

Length (cm) Width (mm) Year n average average 2002 20 5.50 2.85 2003 35 7.64 2.89 Peduncle length in ‘KN30-8’ is not significantly different from that in plants of C. kousa or C. nuttallii but the peduncle length is clearly longer than that of the one known F₁ interspecific hybrid of C. kousa×C. nuttallii in commerce as ‘KN4-43’ (U.S. Plant patent application Ser. No. 10/741,618) having an average length of 1.67 mm.

FLORAL BRACTS

-   Number: Typically 4 (in two opposing pairs; infrequently 5). -   Size of floral bracts:

Length of upper Width of upper Involucral spread bracts (cm) bracts (cm) (cm) Year n average average n average 1993 50 6.89 5.26 25 14.28 1997 20 8.06 6.32 10 16.52 1999 94 7.49 5.31 47 15.41 2002 40 7.20 6.10 20 14.68 2003 70 8.90 6.74 35 18.18 Length of lower Width of lower Involucral spread bracts (cm) bracts (cm) (cm) Year n average Average n Average 1993 50 6.86 5.61 25 14.22 1997 20 8.01 6.43 10 16.41 1999 94 7.27 5.76 47 15.00 2002 40 7.20 6.57 20 14.71 2003 70 8.72 6.72 35 17.83 The size of the floral bracts on plants of ‘KN30-8’ varies from year to year due to the many environmental factors influencing the annual growth of trees. However, the floral bracts of our new hybrid are larger than those of any cultivar of C. kousa known to us and are larger than those of the six patented F₁ interspecific hybrids of C. kousa×C. florida (‘Aurora’® U.S. Plant Pat. No. 7,205, ‘Celestial’® U.S. Plant Pat. No. 7,204, ‘Constellation’® U.S. Plant Pat. No. 7,210, ‘Stardast’® U.S. Plant Pat. No. 7,206, ‘Stellar Pink’® U.S. Plant Pat. No. 7,207 and ‘Ruth Ellen’® U.S. Plant Pat. No. 7,732) in the trade today as well as the one and only F₁ interspecific hybrid of C. kousa×C. nuttallii (‘KN4-43’, plant patent applied for) and the F₁ interspecific hybrid ‘Eddie's White Wonder’ (C. florida×C. nuttallii) U.S. Plant Pat. No. 2,413. The floral bracts of ‘KN30-8’ are comparable in size to those of typical plants of C. nuttallii (bracts about 6 to 7.5 cm).

-   Color:     -   -   Adaxial surface.—Closest to 155A White Group.         -   Abaxial surface.—Closest to 155D White Group. -   Shape: Globose. -   Apex: Broadly apiculate. -   Base: Attenuate. -   Bract stalk length: 5 to 8 mm. -   Bract stalk width: 5 to 6 mm. -   Flower description: Very floriferous. Single flowers arranged in     compact, dense heads subtended by the large floral bracts. No     observed fragrance. Flowers not persistent. Floral display of the     involucral bracts lasts about two to three weeks, depending on     weather conditions. -   Flowering habit: Anthesis of the tiny, relatively inconspicuous true     flowers generally begins a few days following the onset of the     ornamental display of the large floral bracts which generally occurs     in central New Jersey about the last week of May and continues for     14 to 21 days depending on the prevailing weather conditions. Floral     development is asynchronous within the inflorescence. -   Number of true flowers per flower head:

n 1995 73.1 25 1996 69.7 10 1997 64.9 58 1998 67.3 14 1999 74.1 47 2001 72.0 25 2002 63.7 41 2003 69.4 35 The number of true flowers per flower head of our advanced generation interspecific hybrid is intermediate to that of the parent plants as the pistillate parent had about 70-80 flowers per flower head and the staminate parent (C. kousa) about 45-55 flowers per flower head.

REPRODUCTIVE ORGANS

-   Stamens:     -   -   Number per flower.—4.         -   Color.—Somewhat greenish white.         -   Filament size.—Approximately 2.5 mm long and 0.5 mm wide.         -   Anther size.—Approximately 1.1 mm long and 0.25 mm wide.             Pollon is sparse in amount, and is somewhat brownish yellow. -   Pistil:     -   -   Number.—1.         -   Diameter.—Approximately 0.75 mm.         -   Color.—Somewhat brownish yellow.         -   Style plus stigma.—About 2.25 mm long.

FRUIT

-   Flower head with fruit: Fruits are 2-celled, typically 1 seeded,     fleshy, drupes that form a mounded raspberry-like syncarp     approximately 2.5 cm in height and 2.5 cm in width with a flattened     base. The many inferior ovaries are enclosed in a fleshy mass     similar to the fruit of C. kousa. The exterior surface is quite     smooth except for the dried floral parts at the tip of each     individual inferior ovary; i.e., the sepals and the style and stigma     which collectively appear as a minute brownish blotch (177A     Greyed-Orange Group) in the mature fruit. -   Seed:     -   -   Color.—165C Greyed-Orange Group.         -   Size.—6.5 mm long and 4.0 mm wide at center. Is basically             rounded but narrows to an obtuse end at the base. 

1. A new and distinct cultvar of dogwood tree, substantially as herein shown and described, comprising an advanced generation interspecific hybrid of Cornus kousa×C. nuttallii with C. kousa. 